Machine displays E11 and does not recognize the water tank or reports it as empty even when full.

Safety first: Disconnect the machine from mains before inspecting internal sensors.

Step-by-step:

• 1. Check tank float: Remove the water tank and look for the plastic float inside (often with a small magnet). Ensure it moves freely up and down and is not stuck by scale. Clean the tank thoroughly.
• 2. Clean sensor window: If your Siemens model uses an optical level sensor, clean the transparent window on the tank and the corresponding area on the machine.
• 3. Test magnet function: With the tank removed, hold a small magnet near the sensor area on the machine (usually where the tank sits). If the machine now detects a tank, the float magnet in the tank may be weak or missing.
• 4. Inspect sensor (advanced): Remove the side or front panel to access the reed switch or Hall sensor. Check for loose connections or damage.
• 5. Replace faulty parts: Replace a damaged tank or sensor with Siemens-approved parts. If unsure, have a Siemens technician perform the repair.